troubleshouting TCP session for DLSW_question1

[jabouaf]

Hello,

Having TCP session problem between 2 routers (DLSW), I get a "show tcp".

For the high TCP session (port 2065, DLSW with prioritization) I have some "GiveUp" started timer.

Can someone explain me what is this timer for ?

Stand-alone TCP connection to host x.y.z.t

Connection state is ESTAB, I/O status: 1, unread input bytes: 0

Local host: a.b.c.b, Local port: 11085

Foreign host: x.y.z.t, Foreign port: 2065

Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)

TCP driver queue size 0, flow controlled FALSE

Event Timers (current time is 0x293BA7C8):

Timer Starts Wakeups Next

Retrans 2270 0 0x0

TimeWait 0 0 0x0

AckHold 2261 0 0x0

SendWnd 0 0 0x0

KeepAlive 0 0 0x0

GiveUp 2269 0 0x0

PmtuAger 0 0 0x0

DeadWait 0 0 0x0

iss: 2530872096 snduna: 2530900678 sndnxt: 2530900678 sndwnd: 20042

irs: 444304397 rcvnxt: 444332070 rcvwnd: 20372 delrcvwnd: 108

SRTT: 300 ms, RTTO: 607 ms, RTV: 3 ms, KRTT: 0 ms

minRTT: 8 ms, maxRTT: 300 ms, ACK hold: 200 ms

Flags: higher precedence, retransmission timeout

Datagrams (max data segment is 536 bytes):

Rcvd: 4531 (out of order: 0), with data: 2261, total data bytes: 27672

Sent: 3002 (retransmit: 0), with data: 2269, total data bytes: 28581

Regards,

[mbinzer]

Hi,

dlsw set a TCP giveup timer, which is started each time the TCP retransmission timer is started for a new window of data. If the give up timer had expired before the packet is ACKed, the TCP connection will be closed.

Dlsw is explicitly setting the tcp giveuptimer. By default it is 3 * dlsw peer keepalive.

The dlsw peer keepalive is by default 30 seconds which gives you a default tcp giveup timer of 90 seconds.

Again what that means is if a tcp segment is not acked after 90 seconds tcp is closing this tcp connection.

The timeout is configurable on the dlsw remote peer statement with the timeout option.

That is sort of a savegurard against a broken network and tcp is not detecting it fast enough.

thanks....

Matthias

[jabouaf]

Hello Matthias.

Thank you for this explaination.

Best Regards.

Jean-david